1.6TB Getting Ready for Prime Time

Over the past 18 months, the VIAVI ONE LabPro® ONE-1600 has supported customers that are bringing 1.6Tb OSFP 1600 modules to market. Challenges initially focused on PHY layer and 224G SERDES, but we now move into a more rigorous, standards-backed phase as advanced features such as APSU/ILT, inner FEC, and CMIS all must be developed, debugged and interop’ed.

The next stage of 1.6Tb moves us from first samples to mainstream products that must scale into the millions and interop across multiple vendors, while meeting the needs of standards and MSAs.

IEEE 802.3dj at D2.4

IEEE 802.3dj is now at D2.4 with clarity and detail on the key aspects of 200G/lane signaling supporting 200GbE, 400GbE, 800GbE and 1.6TbE Ethernet rates, and module MSAs and OIF CMIS all evolving as 1.6TbE hits prime time.

Several new additions to 802.3 have been added in dj to support the challenges of 200G/lane signaling and scaling to 1.6TbE Ethernet.

Each of these new additions must be developed, debugged and validated to ensure compliance and interoperability across a multi-vendor ecosystem.

ILT and APSU – Optimal Settings of Channel Equalizers

ILT is one of the most talked about new aspects of 802.3dj, and it is key to enabling 200G/lane links to be deployed at scale. It replaces the concept of a high loss/low loss channel, from host to module and across the link. This autonomous path start-up (APSU) combined with intra-sublayer link training (ILT) allows optimal settings of channel equalizers for lowest error floor and most reliable link performance.

Annex 178b builds on the widely deployed and successful link training used for DAC cable support but adds a new layer of complexity. This doesn’t just impact the PHY SERDES, but also in CMIS and other management features. Any approach to development, validation and interop of APSU/ILT must be multi-domain with PHY, L1 and CMIS all brought together in any test and measurement approach.

VIAVI builds on our experience with 200G SERDES bring-up and our generations of DAC support and debug. When used together in our integrated applications, the end user gets an insightful, multi-domain view critical for debugging and validation.

Inner FEC – an Additional FEC Inside the Optical Module

While 500m DR/FR links will be the dominant PMDs, there are multiple applications for -2 variants, 2km loss budget.  This requires an additional ‘concatenated’ FEC, which provides additional coding gain for the optical link. This inner FEC is inside the optical module and can be normally selected when advertised as one of the app-sel codes.

VIAVI offers comprehensive and complete coverage for iFEC validation, as well as the integrated applications on our ONE LabPro platform.  In addition, our optical MAP-300 platform has complete visibility and control of the optical, CMIS and PHY/data layers.

From 25G PCS Lanes at 800GbE to 100G PCS at 1.6TbE

1.6TbE Ethernet shifts from the 25G PCS lanes used at 800GbE and below to 100G PCS lanes. This is again a new aspect of 802.3dj.   VIAVI applications for PCS and FEC give complete coverage of all aspects of 1.6TbE Ethernet validation and debug, which means every aspect of the PCS including alignment markers and FEC symbols can be manipulated and analyzed in one application.

Symbol Muxing in the Gearbox

Symbol muxing is another important aspect of 802.3dj. In previous generations of Ethernet, bit muxing was used to build up the PAM-4 symbol, but dj muxes at the 10bit FEC symbol level. While adding complexity, it does add coding gain, a valuable aspect when operating at 200Gbs per lane.

An Integrated Approach to Test & Measurement at 1.6Tb

These new challenges, combined with the need to scale 1.6Tb faster than any previous Ethernet rate, mean an integrated and complete multi-domain approach is required in test and measurement. Since September 2024, VIAVI has been delivering 1.6Tb class solutions. This experience, combined with our multi-domain applications and portfolio, helps our customers deliver 1.6TbE products which scale and interop across a multi-vendor ecosystem.

The ONE LabPro ONE-1600ER module extends the capabilities of the ONE LabPro platform with full Ethernet support based on the latest 802.3dj specification

Advanced Layer 0-7 AI Fabric, Network and Security Test Solutions

While ONE LabPro secures the link foundation, the newly-acquired TestCenter family of products centers on the massive scalability and protocol complexity of the network fabric. Along with CyberFlood, VIAVI has the ability to validate networks with full stack traffic, all the way up to Layer 7.

See Us at OFC26

Catch these solutions in action at OFC 2026 in Los Angeles, CA, March 17 – 19, Booth 1239.  Not attending? No worries!  Visit our OFC page or submit a meeting request and we’ll connect at your convenience.  Schedule a Meeting: VIAVI at OFC 2026

Real-world Testing Insights – View our 1.6Tb Content

• How AI is Pushing the Boundaries of Data Center Networks
• 224G SERDES – The Foundation of Hyperscale Data Centers, AI and HPC Applications
• 1.6Tb/s Module Development and Validation – Initial Impressions
• Anatomy of a 1.6Tb Module 
• Testing at 1.6T – Enabling AI, ML, HPC and Quantum Applications at Scale
• ONE-1600: Cutting-edge, Field-proven 1.6T Testing Solution
• ONE-1600 Accelerates Development of 1.6T Optics at Scale
• Scale with Confidence-Delivering on the Promise of the AI Revolution